1 files changed, 41 insertions, 0 deletions
diff --git a/plotter/parse.py b/plotter/parse.py
new file mode 100755
index 0000000..473e196
--- /dev/null
+++ b/plotter/parse.py
@@ -0,0 +1,41 @@
+
+import math
+import copy
+
+
+# create list of "safe" methods to allow in equations
+_safe_dict = {
+    "__builtins__": {"__import__": __import__},
+    "abs": abs,
+}
+
+# grab desired methods from math library
+_math_funcs = ['ceil', 'floor',
+    'exp', 'log', 'log10', 'pow', 'sqrt',
+    'acos', 'asin', 'atan', 'atan2', 'cos', 'hypot', 'sin', 'tan',
+    'cosh', 'sinh', 'tanh',
+    'pi', 'e'
+]
+for symbol in _math_funcs:
+    _safe_dict[symbol] = getattr(math, symbol)
+
+
+def parse(stringfunc):
+    """Returns a method corresponding to stringfunc."""
+
+    # create a function using user input as the return line
+    stringfunction = ("from __future__ import division\n"
+        "del __builtins__['__import__']\n"
+        "def plot(x):\n"
+        "    return %s"
+        % stringfunc.replace("^", "**"))
+    compiledfunction = compile(stringfunction, "<string>", "exec")
+
+    # plot the method using "safe" globals and locals
+    # http://lybniz2.sourceforge.net/safeeval.html
+    # this should also be thread-safe (I think...)
+    globalscopy = copy.deepcopy(_safe_dict)
+    localscopy = {}
+    exec compiledfunction in globalscopy, localscopy
+    return localscopy["plot"]
+